The practice of recording vehicle and accident data in a nonvolatile memory in the vehicle shortly before, during and after an accident is becoming increasingly important. These data are intended to assist with being able to reconstruct the accident and its cause as accurately as possible. Such systems are also of interest to insurance companies who wish to use the data to determine insurance payments in the event of damage. Furthermore, legal provisions for recording accident data have been proposed by various authorities (for example the National Highway Traffic Safety Administration) and other organizations.
Existing systems are not designed to store a relatively large quantity of data. Certain components of a vehicle, for example the airbag ECUs, must have a power supply which is independent of the vehicle's power supply in the event of the vehicle's power supply failing on account of an accident. For this purpose, an “emergency power supply” is ensured in known systems with the aid of electrolytic capacitors.
However, the operation of storing a relatively large quantity of data in a nonvolatile memory can take up a relatively large amount of time, for example two seconds. A very large number of capacitors and very large capacitors would be needed to maintain the power supply for the airbag ECUs over such a long period of time, which would make the overall system appreciably more expensive.
There is therefore a need for a new concept of an airbag ECU having a data recorder unit (a so-called “event data recorder”) which manages to ensure the power supply with the smallest possible number of capacitors in the event of an accident.